A. Acylated alpha-Hydroxy Fatty Acid Esters of Glycerol
U.S. Pat. No. 2,652,410 to Cunningham et al., issued Sept. 15, 1953, discloses the preparation of alpha-hydroxy acids and their estolides (esterification product of two alpha-hydroxy acids) by the oxidation of petroleum waxes. The alpha-hydroxy acids have from about 5 to 30 carbon atoms per molecule while the estolides have from about 10 to 60 carbon atoms per molecule. These acids and estolides are obtained by oxidation of mixtures of straight chain paraffins containing between 15 and 50 carbon atoms per molecule, preferably about 20 to 35 carbon atoms per molecule. The estolides can be dehydroxylated to form an alpha, beta unsaturation. These alpha-hydroxy acids and estolides can be esterified with various polyols, including glycerol, to provide semi-solid or solid products for linoleum cements and drying oils. See, in particular, Examples VI, VII, IX and X. See also U.S. Pat. No. 2,721,188 to Polly et al. issued Oct. 18, 1955, which has a similar disclosure.
B. Low-Calorie Substitute Fats Based on Glycerol Esters
U.S. Pat. No. 3,579,548 to Whyte, issued May 18, 1971, discloses glycerol esters of alpha-branched carboxylic acids having the formula: ##STR3## where X is an alpha-branched carboxylic acid residue having the formula: ##STR4## where R.sup.1 and R.sup.2 are C.sub.1 -C.sub.30 alkyl groups, R.sup.3 is hydrogen or a C.sub.1 -C.sub.30 alkyl group, the total number of carbon atoms for R.sup.1 +R.sup.2 +R.sup.3 being from 8 to 30 and Y and Z are X, OH, or ##STR5## where R.sup.4 is a C.sub.8 -C.sub.30 alkyl or alkenyl group. These glycerol esters of alpha-branched carboxylic acids have the physical properties and utility of standard triglyceride fats but are less digested or absorbed. See also D. Hamm, "Preparation and Evaluation of Trialkoxytricaballyate, Trialkoxycitrate, Trialkoxyglycerolether, Jojoba Oil and Sucrose Polyester as Low Calorie Replacements of Edible Fats and Oils," J. Food Sci., Vol. 49, (1984), pp 419-28, which discloses the use of trialkoxycitrate or trialkoxytricarballyate as low calorie replacements of conventional edible fats and oils.
C. Substrate Specificity of Pancreatic Lipase
Brockerhoff, "Substrate Specificity of Pancreatic Lipase: Influence of the Structure of Fatty Acids on the Reactivity of Esters," Biochim. Biophy. Acta, Vol. 22, (1970), pp 92-101, describes the results of studies where various monoesters of aliphatic acids were hydrolyzed with pancreatic lipase. It was found that methyl or like substituents, or unsaturation, at the 2 to 5 carbon atoms of the acid led to a relative resistance of the esters against lipase.